Tenacity is a key word for cacti and succulents. They make a good choice of plant for gardeners who lack the knack that sees plants flourish, but who yearn for something green in their immediate surroundings. They are also very good subjects for indoor container growing, and can prove a successful introduction to gardening for young people: I still remember with affection the “mother-of-millions” (Kalanchoe daigremontiana) succulent I was given by a neighbor when I was a pre-teen.
All succulents have the virtue of tolerating an erratic watering schedule, since that is what nature provides them and what they have adapted to manage; but some have the additional virtue of tolerating dimly lit growing conditions, which is indeed a bonus if you are looking for a house plant to keep an invalid company. Ideally, some rotation of plants from poorly lit to window sill locations will increase the probability of achieving flowering: but that does require additional discipline on the part of the gardener.
There are some cautions to be observed with growing any plants on a window sill (or any other surface close to a window). On a sunny day temperatures close to the glass can exceed 100?F; and in winter, without insulation or adequate air movement plants can literally freeze.
The flowers of many succulents and cacti are, of course, their crowning glory. Some are truly spectacular. A relation of mine on occasion looks positively smug, considering the lack of effort involved, as her crab cactus (Epiphyllum truncatum) burst into their annual riot of flowering. Each flower comes close to the size of the plant itself. Orchid cactus (Disocactus ackermannii) is another cactus that produces prolific and vibrant flowers. But size isn’t everything, and there is also pleasure to be had in contemplating the tiny but perfectly formed flowers of Crassula nudicaulis.